1. Technical Field
This invention relates generally to the field of thermometric diagnostic devices and methods, and more particularly, to an apparatus and method for sensing, recording, and indicating thermal irregularities across a dermal surface.
2. History of Related Art
Foot problems are the major cause of amputation and physical disability in patients with diabetes. Yet studies have shown that simple techniques such as identifying patients at risk for foot ulcers and educating these patients about proper foot care can help prevent such serious complications.
Preventing diabetic foot problems requires careful monitoring of the patient's feet on a regular basis. Unfortunately, the daily inspection of the plantar and dorsal surfaces of the feet require some manual dexterity and experience, and some patients may be hampered in their ability to conduct regular inspections because of obesity, arthritis, or poor eyesight. Often, mirrors or teaching a friend or family member to conduct the inspection are required.
In addition, a necessary component in the causal pathway to foot complications in persons with diabetes is peripheral sensory neuropathy. Damage to sensory feedback concerning position and tactile stimulation of the foot provides an environment where skin, ligaments, or bones of the foot can be injured without any knowledge by the patient that such injury has occurred. For instance, areas of high pressure on the sole of the foot normally become irritated and inflamed because of normal walking activities. Persons with normal pain sensation will stop or modify their activities to avoid pain and subsequent ulceration, or other damage. However, in diabetics with nerve damage the sensation of pain is often absent, and activities are often continued until the injury is so prominent that amputation is required.
Degenerative arthritis, bunion deformities, or hammer toes, as well as other foot deformities, increase the risk of developing an ulcer on the foot. Such physical alterations in the structure of the foot can produce high pressure areas, which in turn produce inflammation, tissue destruction, and ulceration. Once again, without the early warning signal provided by normal pain sensation, tissue damage may become quite advanced before reaching a level noticed by the patient. Unfortunately, by the time that such knowledge occurs, amputation may be required.
Prevention and treatment of ulceration can be quite effective in preventing lower extremity amputation in diabetics. Prevention strategies focus on protecting the sole of the foot from high pressure areas, and detection of early signs of tissue injury. Objective methods of implementing these strategies, which often involve measurement of inflammation and foot pressures, have historically been expensive, bulky, or relatively unavailable to physicians and their patients. However, it has been found that an increase in local skin temperature is one of the earliest indications of tissue injury or inflammation. Therefore, monitoring the skin temperature on a monthly basis by physicians and more important, on a daily basis by patients, can provide an easy, inexpensive, and readily quantifiable way to detect areas of the foot that are at risk of ulceration.
The most common method of evaluation and diagnosis for foot temperature involves manual manipulation of the feet with a single hand to find a warm area or "hot spot." The high temperature area is compared with the rest of the foot, and the corresponding bilateral location on the other foot. A temperature difference of more than 2.degree. C. is clinically significant, and is held to be detectable by the average practitioner. However, physicians and others with temperature-insensitive hands, or circulation problems of their own may not be able to reliably detect such small changes in temperature.
Various instruments have been devised to detect skin temperature, but these are often expensive, or formed for use in the ear, or for general use, and do not lend themselves to use with the foot. The display may not be visible to the user if applied to the sole of the foot; there is also no sure way to determine sensor proximity to the foot, or provide any type of scanning function which can be monitored by the user as areas of lower or higher temperature are encountered. Finally, such devices are ordinarily constructed so as to measure the temperature of any surface encountered; whether the temperature measurement is relevant to skin, or to some other surface within the field of view of the sensor, is not detected by the instrument.
Therefore, what is needed is an apparatus and method for easily, inexpensively, and repeatedly detecting temperature differences along the sole of the foot of about 2.degree. C. or greater. Further, such a device and method should lend themselves to continuous scanning of the surface of the sole, along with reliable determination of the presence of an anatomical surface in front of the sensing element. Such a device and method which provide both visual and audio indications or alarms to the practitioner and/or patient would also be desirable for persons hampered by poor vision or poor hearing.